[Health Column] Walking Is My Strength

During winter like these days, the time to bask in sunlight is short. It is easy to curl up indoors to avoid the cold. Motivation decreases, physical activity reduces, appetite diminishes, and sleep becomes difficult. The body aches here and there without any particular reason. It is a season prone to depression if not careful. Seasonal depression is a type of depression that appears only during specific times of the year.

It occurs especially when the days are short in winter and exposure to sunlight decreases. Seasonal depression is common in regions with high latitudes where winter daylight hours significantly decrease, while it is less common near the equator where changes in daylight are minimal. The exact cause of seasonal depression is not yet clearly identified, but it is believed to be related to abnormalities in the brain's "biological clock."

How can we overcome the gloomy feelings during this cold and dark season? A Japanese study measured brain blood flow using infrared sensors on people pedaling a bicycle. Just 15 minutes of cycling increased the activity in brain circuits responsible for emotion regulation and the levels of serotonin, a neurotransmitter. Dysfunction of serotonin is closely linked to depression. In depressed patients, serotonin activity is reduced. Another experiment was conducted in a hospital in the United States, where the amount of sunlight in each patient room was measured for patients recovering from spinal surgery. Doctors found that patients moved to rooms with bright sunlight had higher pain tolerance and required less pain medication.

Bright sunlight helps serotonin production, enhancing willpower. It boosts motivation and lifts mood. Moreover, it promotes melatonin secretion, improving sleep quality. Since the British have few sunny days throughout the year, people of all ages enjoy sunbathing even with small rays of sunlight peeking through clouds. This might be an instinctive human behavior to overcome depression. In fact, hospitals use light therapy to treat depression. Light therapy involves exposure to 10,000 lux of bright light for 30 minutes to an hour early in the morning to regulate the sleep-wake circadian rhythm and improve depressive symptoms. Exercise, sunlight, serotonin, and depression are closely interconnected in this way.

It has been revealed through various neuroscience studies that when life changes positively, our brain neurons also change positively. The brain's electrical activity, chemical composition, and ability to generate nerve cells all change. When the brain changes like this, brain circuits are recalibrated, leading to further positive life changes. For example, exercise alters the brain's electrical activity during sleep, which in turn reduces anxiety, improves mood, and generates more energy to exercise. Similarly, expressing gratitude produces serotonin, which improves mood and helps break bad habits, leading to more reasons to be thankful. In other words, actions change the brain, brain changes alter mood, and ultimately this leads to a virtuous cycle that transforms life.

Now that we know the method, let's put it into action. Although it is still chilly, do not stay indoors all the time; go outside for at least a few minutes during midday. Taking a walk or listening to music under the sunlight is also good. There is an old saying that losing money is a small loss, losing honor is a big loss, but losing health is losing everything. Let's go outside. Let's bask in the sunlight. And let's walk. Both body and mind will become healthier.

Seongwon Noh, Professor, Department of Psychiatry, Hanyang University Hospital